Method for hardening camshafts and the like



-Oc't. 3-1, 1939. J. D. JUDGE 2,178,281

' METHOD FOR. HARDENING CAMSHAFTS Ania THE LIKE Filed Oct. 9, 1935Patented. Oct. 31, 1939 METHOD FOR HARDENING GAM SHAFTS AND THE LIKEJoseph D. Judge, Hamilton, Ohio, assignor to The Hamilton Foundry andMachine ,Com pany, Hamilton, Ohio, a corporation of Ohio ApplicationOctober 9, 1935, Serial No. 44,164 1 Claim. (01. 148-21) inventionrelates to the art of heat treat ing, .and more particularly to thedifferential treatment of heat treatable cast iron camshafts and thelike. a 5 One of the principal 'objects of the invention is theprovision of a simple and effective method of differentially heattreating cast iron articles such as camshafts and the like to alter thephysicalcharacteristics'of such articles to different and desireddegrees at spaced points therein. v I

Another object of the invention is the provision' of a method ofdifierentially treating cast .iron camshafts to import the desiredhardness to .localized areas thereof arid to refine the material atother portions A further object of the invention is the provision ofapparatus for carrying out this method. Other objects and advantages ofthe invention willbe apparent fromthe following description,-

the accompanying drawing and the appended claim. I

In the drawing, which discloses a preferred embodiment of theinvention-- Fig. 1 is an el evational View of a camshaft of thecharacter upon which this invention is prac- 'ticed;

Fig. '2 is a side elet ational view of a supporting structure used inthe heat treatment of the camshaft of Fig. 1;

Fig. 3 is a transverse sectional view as indi-,

cated by the line 3--3 of Fig. 2; v

Fig, 4 is a diagrammatic showing of one stage ofthe heat treatingoperation; and Fig. 5 is a diagrammatic showing'of a modifiedarrangement of the quenching jets.

The drawing, in which like characters of reference designate like partsthroughout the several views thereof, illustrates a method of heat treat40 ing articles of cast iron, and more particularly for treatingc'amshafts which have been cast from an iron that is subject to heattreatment. The use of such materials, heat. treated in accordance withthe present invention, widens the field of usage of cast iron bypermitting the sub stitution of this relatively inexpensive material forthe more costly'steels. material preferably used in, accordance withthis invention, this material being a cast iron in which the graphite iscontrolled by adjusting the chemical composition to a point where thecasting would normally be white iron, and then causing all carbides overthe amount necessary'for pearlite to .decompose into diffused particlesof Meehanite is the graphite by the addition of measured amounts ofcalcium silicide.

In utilizing such materials for camshafts, of which an illustrativeexample is shown at .l0- in the drawing, and which comprises integrallyformed cams l I, bearings l2, a gear l3, and an eccentric H, thedifierence in the physical requirements of the different parts ,of theshaft necessitates a difierential treatment so that those parts subjectto extreme wear will have the 1" required hardness and those otherportions, such as the bearings, gear, etc., will be refined to thedesired degree but permitting the machining of these parts after thisrefining has taken place. In theapractice of this invention the camshaft is heate to a suitable temperature above the critical temperature,the localized areas required to be hardened very hard are then subjectedto, a localized Water mist quenching operation which is of suchcharacter that the-hardening extends '5 over only a desired limited areaand depth, after which the entire article issubjected to a quenchingoperation to fix or retain the properties currently existing in theshaft. The relationship of the successive steps of the treatment is such25 that during the initial quenching of the localized areas, such. asthe cam lifts, the temperature of the remaining portions falls from theinitial high temperature at which localized quenching 1 begins tosuitable temperature such that subse- 30 quent rapid quenching of theseremaining portions results in a desired toughening and refining of suchcharacter that the last quenched parts remain machinable.

I n order that the hardening may be of con- 35 trolled extent and depth,the initial quench'ng operation which serves 'to harden the localizedareasis arranged tobe readily controllable so that the rate .of heattransfer, while quite fast so as to afiord a' quenching operation toinduce the desired degree of hardness, is regulated in accordancewith'the proportioning and bulk of the article. That is to say, theabsorption of heat by the quenching medium at,the localized" 4 ment withanother of the arms as indicated at 21..

quenching the hardened area is restricted as desired.

Hardening of this character obtains through. the use of water chargedair blasts which are simultaneously directed only against the portionsof the cams that are to be hardened. The characteristics of the blast,that is, the temperature of the air and the quantity of water entrainedtherein is coordinated to the physical proportions of the shaft tothereby regulate the quenching rate. A complete treatment of the shaftoccurs with one heating thereof.

To carry out this method of heat treatment, and to properly andaccurately direct the quenching blasts to the desired points, a frame isprovided which is arranged to hold the heated shaft in a predeterminedpositioning or, range of positioning. As shown, the frame comprises abase 2i having means centrally located thereon as indicated at 22 forthe receptionand centering of'one end of the camshaft H), which ismounted vertically in the frame. The base 2| carries two spaced locatinglugs 24 which cooperate with a lug 24' fixed on the camshaft to positionthe camshaft in predetermined approximate position permitting somelimited variation in position about the camshaft axis. Angularly spacedwith respect to the center support 22, and projecting upwardly from thebase 2|, are a plurality of arms 23; each of which has provision forsupporting nozzles in proper operating relationship with the cam areasthat are to be hardened. Additional support is provided for centrallocation of the shaft within the holding frame and is shown ascomprising an arm 25 .pivotally mounted at 26 from one of the upstandingarms 23 and arranged to be held in latching engage- The pivotallymovable arm 25 is provided with shaft engaging means such as thecentering pin 28 which interfits a centering hole in the end of the camshaft.

The upstanding arms 23 are shown as being of different heights; theextent of these arms being determined by the positioning of the camswhich in turn govern the positioning of the nozzles carried by thedifferent arms and which direct the quenching blasts. The nozzles, whichare located in predetermined position coordinated with the campositionings, are each ,attached to a source of air under pressure andto a fluid supply for introduction of a water stream or mist direct-. 1yagainst the cam lifts. To clarify the showingof Fig. 2 the completeconduit connections to the plurality of nozzles has been omitted andonly short conduit sections are illustrated to avoid a multiplicity oflines thereon. the nozzles 30 has a conduit II and a conduit 32coiinected respectively to a source of air under pressure and a watersupply tank. As shown in the diagrammatic illustration' of Fig. 4, allof the air conduits 3] have a common connection to a control valve 33which is connected to any suitable air pressure source. The waterconduit 32 has a valved connection l'llto a water supply tank 28 whichis preferably provided with means such as pump 34 for creating asuitable small pressure. The arrangement of the nozzle may be such thatwater or a mixture ofwater' and air '70 in the desired proportions issupplied under pressure by regulation of valves in the supply lines, orthe arrangement may be such that the water is entrained in the air blastmerely by an aspirating action. The arrangement of eachnozzle is suchthat it is accurately positioned with respect As shown, each of to thecam lift associated therewith when the lug 24 is positioned midwaybetween lugs 24, so that the air blast is directed against the point ofthe cam lift as is shown in Fig. 4. Limited movement of the shaft aboutits own axis while the blast is eflective provides a hardened surfaceadjacent the point of the cam as well as hardening the point itself.

In the practicing of this invention the camshafts are first heated to atemperature above the critical temperature. when using a material of thecharacter mentioned the critical temperature on cooling is of the orderof 1350 F. The temperature to which the camshaft is raised is of theorder of 1600 F. Quenching of the 10- calized areas, or cam lifts, thatare to be hardened takes place from a temperature that approximates thishigh temperature and continues until the temperature of the remainingportions I of the shaft has fallen to a point at which suitable reflningand toughening will occur. The temperature at which the second quenchingoccurs is selected in accordance with the required hardness propertiesfor any particular work piece, but is preferably at a temperature of theorder of 1000 F. for the. particular material referred to.

As mentioned in general terms above, the quenching blast onthose partsthat are to be greatly hardened continues while the remainder of theshaft is cooling to a suitable temperature for quenching, and itwill beapparent that proper regulation of the quenching blasts as by adjust--ment of their time of duration will control the characteristics of theother parts of the shaft, when those other parts are quenched as byimmersion in water. On shafts in which the areas to behardened are largeas compared to the bulk 'of the shaft the rate of heat transfer will bedifferent than in shafts wherein the hardened areas are small ascompared to the general proportions of the shaft. In either instance therate of heat transfer produced by thewater blasts is such as to providea temperature drop rapid enough to produce hardening.

The duration and rate of the localized water blast quench is such thatwhen the'untreated portions have reached a suitable temperature, thoseportions which have been subjected to the localized hardening quenchwill have dropped to a low temperature of the order of 200 F. In orderthat an objectionable drawing of the hardened areas may not occur thesecond or immersion quench takes place very quickly after discontinuingthe quenching blasts and before an objectionable heat (transfer can takeplace within the shaft toward the hardened areas.

The time interval between the initial quenching of the parts that are tobe very hard and the subsequent quenching of those parts that are to betoughened and refined may vary somewhat,

depending on the character of the work piece. The temperature'of thework piece begins to fall as soon as it is removed from the furnace.Those parts subjected to localized quenching may have a very rapidtemperature change. The rate of temperature change of those parts notsubiected to quenching will be influenced by the nearness of such partsto the quenched areas, by the relative bulk of the quenched andunquenched parts, by radiation, by the accessibility of the parts to airconduction and such factors. In order that the subsequent quenching mayoccur at a proper temperature, or at properly re- I lated temperaturesin the wbrk piece, it may be desirable in sgme instances as, forexample, in

. 2,178,281 "a bearing or m a part of the shaft of large bulk which willhave a slow normal cooling, to induce a more rapid cooling by artificialmeans such, for example, as by directing one or more air blasts on theparticular parts of the work piece. The rate of temperature changeresulting from the application of the air blast is such as to notproduce a quenching action, and it may be so regulated that at thetermination of the initial quenching the temperature of the part orparts subjected to the air blast will be a proper one for subsequentquenching. The air blast may also function to accelerate the temperaturedrop of certain portions so that upon subsequent quenching those partswill be at a lower temperature than other parts not subjected to initialquench ing so that at the time of subsequent quenching several differenttemperatures exist in the work piece and correspondingly differentdegrees of hardness will result from quenching.

As an illustration of the application of an air blast attention isdirected to Fig. 2 wherein one of the arms 23 of the frame 20 is shownas having a nozzle 40 that is directed toward the shaft bearing portionl2 which stands at the lower part of the shaft as mounted in the frame.The nozzle 40 has a connection ll to the source of air supply and toprovide a desired regulation of the air flow and coordinated rate oftemperature. change a valve may be incorporated as in dicated at 42. Itis pointed out that the single nozzle shown is but an illustrativeexample and that a plurality of the nozzles may be used and may bepositioned as desired. 1

The bearing I2, being of relatively large bulk as compared'to theremainder of the shaft. and being more remotelypositioned with respectto the .water mist quenching blasts than the gear l3 for example wouldhave a normal cooling at a slower-rate than the gear referred to. Theapplication of an air blast at this point affords a regulatedtemperature drop permitting subsequent quenching at a desiredtemperature.

localized hardening of the cam lifts may be accomplished by the use of aplurality of quenching blasts directed at different portions of a cam aswell as by the use of a single blast with accomp nylng cam movement asdescribed above.

Referring now to Fig. 5, an arrangement is shown incorporating a cam IIwith which is associated two nozzles that are placed on opposite sidesof the cam point so that quenching blasts are directed simultaneously toboth sides of the cam. The positioning of these nozzles may be alteredin accordance with the desire to harden more or less of the cam surface.

' Treatment of the character described makes possible the use ofrelatively inexpensive cast iron in fields of service heretoforerestricted to more costly steels. Materials of the character mentionedhave a Brinell hardness as cast of about 210. These materials arecapable of being" hardened up to a Brinell reading of 500.

Through the use of the hardening blasts as described the hardness of thematerial may be readily increased to 475 on the Brinell scale which issuitable for the purpose specified. The subsequent toughening quenchresults in a Brinell hardness of the order of 270 which isadequate toprovide a desired wear resistance to the bearings, gears etc. whileretaining those parts in a state that is readily machinab1e..

While the form of apparatus herein described constitutes a preferredembodiment of the invention, it is .to be understood that the inventionis not limited to this precise form of apparatus, and that changes maybe made therein without departing from the scope of the invention whichis defined in-the appended claim.

What is claimed is:

The method of heat treating a camshaft of.

heat-treatable cast iron which comprises heating the camshaft above itscritical tempera-- ,ture, then. subjecting only the cam lifts to a rapidquenching operation through the critical temperature and to atemperature of only a few hundred degrees F. by air and water forhardening the cam lifts, rotatably moving the camshaft through a'smallangle while said rapid quenching operation is effective, cooling theremainingv portions of the camshaft at a slower rate to a point somewhatbelow'the critical temperature, and then quenching the entire shaft byimmersion.

' JOSEPH D. JUDGE.

